Calculating accurate conductance across model systems to develop techniques for transport across singlemolecular junctions.
The current in a molecular junction is a response property (at weak bias) and requires a nonequilibrium treatment (at finite bias), traditional ab initio methods of quantum chemistry and of groundstate DFT have long been regarded as insufficient. There are many wellknown approaches that have been developed in manybody physics from decades of studying this problem for mesoscopic systems, such as quantum dots. Such methods are often so computationally demanding that they can only be applied to simplified Hamiltonians, such as the Anderson model or a Hubbard chain. Thus they are not firstprinciples and do not produce chemically realistic results, or do so only in an empirical fashion. To fill this gap, a standard approach for performing such calculations within DFT was developed early on and is often referred to as nonequilibrium Green’s function (NEGF). In this model, a groundstate DFT calculation is performed for the system with a bias applied, and then the current through the groundstate KS potential is calculated via the Landauer formalism. The Landauer approach can be derived from nonequilibrium Green’s functions, scattering theory, or Kubo linear response. This generally works well for both metal wires and carbon nanotubes, where conductance is simply the product of the number of open channels times the fundamental unit of conductance. However, in the technologically important area of organic molecules between metal leads, standard model calculations often yield conductances that are one or two orders of magnitude larger than experiment.
We endeavor to further improve and understand the modern methods as well as develop new methods to study the quantum conductance problem.
Publications
[147]  Nonexistence of a Taylor expansion in time due to cusps Zenghui Yang, Kieron Burke, Phys. Rev. A 88, 042514 (2013).
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[138]  Accuracy of density functionals for molecular electronics: the Anderson junction Z.F. Liu, J. P. Bergfield, K. Burke, C. A. Stafford, Phys. Rev. B 85, 155117 (2012).
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[135]  The effect of cusps in timedependent quantum mechanics Zenghui Yang, Neepa T. Maitra, Kieron Burke, Phys. Rev. Lett. 108, 063003 (2012).
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[132]  Bethe Ansatz approach to the Kondo effect within densityfunctional theory J. P. Bergfield, Z.F. Liu, Kieron Burke, C. A. Stafford, Phys. Rev. Lett. 108, 066801 (2012).
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[103]  Density functional calculations of nanoscale conductance Max Koentopp, Connie Chang, Kieron Burke, Roberto Car, Journal of Physics: Condensed Matter 20, 083203 (2008).
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[101]  Pride, Prejudice, and Penury of ab initio transport calculations for single molecules Ferdinand Evers, Kieron Burke, Chapter in Nano and Molecular Electronics Handbook 241 (2007).
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[94]  SelfInteraction Errors in DensityFunctional Calculations of Electronic Transport C. Toher, A. Filippetti, S. Sanvito, Kieron Burke, Phys. Rev. Lett. 95, 146402 (2005).
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[92]  KohnSham master equation approach to transport through single molecules Ralph Gebauer, Kieron Burke, Roberto Car, Chapter in Lecture Notes in Physics 706, 463 (2006).
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[88]  Coordinate scaling in timedependent currentdensityfunctional theory Maxime Dion, Kieron Burke, Phys. Rev. A 72, 020502 (2005).
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[87]  Zerobias molecular electronics: Exchangecorrelation corrections to Landauer\textquoterights formula Max Koentopp, Kieron Burke, Ferdinand Evers, Phys. Rev. B 73, 121403 (2006).
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[85]  Density Functional Theory of the Electrical Conductivity of Molecular Devices Kieron Burke, Roberto Car, Ralph Gebauer, Phys. Rev. Lett. 94, 146803 (2005).
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[69]  Currentdensity functional theory of the response of solids Neepa T. Maitra, Ivo Souza, Kieron Burke, Phys. Rev. B 68, 045109 (2003).
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Funding
We graciously acknowledge support from the Department of Energy (DEFG0208ER46496).
Current Student
Justin Smith

Alumni
Zhenfei Liu

Senior Collaborator
Roberto Car
